Nat
Tom is quite right about the stroke to rod ratio. I have fitted an L20
crank to an L18 years ago by grinding the mains and lightening the
counterweights. It revved easily because of the lighter weights but the rod
angularity caused piston scuffing and basically it was a poor setup.
My suggestion to you is this:
L18W block
Bore 88mm - use Forged flat tops from APEP with 30mm pin height
L14 rods
Stroke crank 2mm on throw - i.e. 4mm stroker (82mm stroke)
This gives a swept volume of 1999cc, stroke:bore of 0.93 and stroke:rod of
1:67 (from memory)
Make sure though that you deck the block and measure everything BEFORE you
order pistons so the pin height is correct and a minimum of machining the
crowns is required to get the pistons to deck. This combo is a rev-machine
and because you have basically spread the changes around it is reliable.
Polish the rods and get them shot peened and have the crank heat treated and
nitrided. Remember that bulletproofing the bottom end is the best thing you
can do as you can set and forget, and concentrate on saving more $$$ to get
the head done.
Hope this helps
Brad Hallett
http://www.powerup.com.au/~bhallett
http://www.datrats.com.au for the best in Nissan Motorsport Equipment
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Tom Richardson
Sent: Thursday, 31 May 2001 1:27 AM
To: [EMAIL PROTECTED]
Subject: Re: 180hp L18 rally motor! Is it possible? Cheap!-TOM
Nat,
Take the rod length and divide by stroke, eg 133/86 = 1.54 It's not the
only thing which makes a revvy motor but it helps.
You could use Z20E pistons, which are the same height as the VG30 pistons
but with a 13cc dish to lower compression and 86mm bore to drop you back
under 2 litres: 1998cc and 9.3:1 with a 39cc head, could shave the deck
0.4mm to bring the pistons up to +0.15, that'd give you 9.6:1 which would
definately run on PULP. Could always weld the chambers up a bit too.
Maybe this is a bit better? These pistons are $215 rrp with chromoly rings
too, it'd be a pretty cost effective engine
- Tom
----- Original Message -----
From: "nat P." <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Thursday, May 31, 2001 12:36 AM
Subject: Re: 180hp L18 rally motor! Is it possible? Cheap!-TOM
> Morning Tom!
> I get it now, cheers for that, How do you work the
> rod/stroke ratio?
> Your combo sounds great, but I cant go over 2 litres
> cos it raises me a class which inturn puts me out of
> the running cos I cant afford the money the big boys
> play with,
> Do you reckon normal PLUP fuel will run 11.5comp. I've
> been told don't go above 10.5comp?
>
> Well being a rally motor I think it would produce good
> torque using those rods.
> Cheers MATE
> Nat
>
>
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